MEXICO CITY — “Poor Mexico, so far from God, so close to the United States.” The comment, attributed to President Porfirio Díaz, has sometimes corresponded with reality, but never more than the present moment. Faith in a loving and present God has always pervaded the daily life of Mexicans. And despite the offenses inflicted upon them across almost 200 years of history, we Mexicans have not really resented the propinquity of the United States nor have we harbored violent nationalist feelings. On the contrary, as people to people, our relations have been fruitful, stable, cordial.

Not anymore. With Donald J. Trump’s electoral victory, every Mexican will have ample reason to entrust himself more closely to God (or the Virgin of Guadalupe) and prepare for a new war, certainly not military, but commercial, economic, ethnic, strategic and diplomatic.

Commercial, because Mr. Trump’s United States may exit Nafta or may impose high tariffs on our exports, to which Mexico will have to retaliate. Economically, if Mr. Trump actually tries to make Mexicans pay for his ridiculous wall by seizing or taxing the remittances of Mexicans working in the States, Mexico will have to respond that such action would be discriminatory and would have to apply to all other immigrants. Ethnic, because of the foreseeable rage that an enormous policy of expelling all undocumented immigrants would unleash, tearing apart families, turning neighbor against neighbor, inflaming differences of identity in the schools. Strategic, because of the disruption of life along the border that would result from even a partial construction of Mr. Trump’s wall.

Confronted with so hostile a government, Mexico could be tempted to cancel agreements that have functioned reasonably well, like our cooperation in matters of security, control of the flow of immigration from Central America or treaties on water rights. A degree of diplomatic tension we have not faced in at least 90 years would accompany the deluge of legal actions that Mexican businesses, individuals and groups — public and private — will start in the courts of both countries as well as internationally to defend their interests.

For Mexico and the United States, Mr. Trump’s victory is a great tragedy. Beyond their governments, Mexicans and Americans have been very good neighbors. Every day, a million people and 370,000 vehicles cross our mutual frontier in an orderly and peaceful manner at 57 border crossings.

Among the many lies spewed by Mr. Trump during his campaign, few were more infamous than his initial assault on the Mexican people: “They’re not sending their best,” he said. “They’re bringing drugs, they’re bringing crime. They’re rapists. And some, I assume, are good people.” The statistics on crime prove him a vicious liar. And though the wave of immigration from Mexico is now basically over, in its heyday we were sending many of our best people to the United States. All they wanted was a route (even if it was gradual and difficult) toward a migratory reform that would give them a legal space to feed their families. Yes, the drug trade is a problem, but drugs cross the border because the market is American, a problem that President Trump shows no inclination to confront.

Average Mexicans fear the brutal effects that the Trump administration is likely to inflict on the economy of their country, the second most important commercial partner of the United States, and the result may very well be a collapse of our fragile social peace. The old and almost forgotten historical wounds will open again, to an awesome extent.

I feel perplexed before the rise of a fascist to the venerable office of United States president. The Greeks knew that democracies are mortal. May the democracy of the United States of America, an example to the world for some 240 years, survive Donald Trump.

Enrique Krauze is a historian, the editor of the literary magazine Letras Libres and the author of “Redeemers: Ideas and Power in Latin America.” This article was translated by Hank Heifetz from the Spanish.